LINIYA, Belarus -- Belarusian President Alyaksandr Lukashenka said there would be no general clampdown on his opponents after an unexplained bomb explosion wounded about 50 people at a concert he attended on July 4 in the capital, Minsk.

No one has claimed responsibility for the blast. The authorities in the ex-Soviet state have played it down, and Lukashenka, who was nearby but unhurt, said he did not see it as an assassination attempt.

He also said the United States had offered technical help in investigating the explosion. Washington has criticized his government for human rights abuses and been involved in a diplomatic spat with Minsk in recent months.

There was no immediate comment from U.S. officials.

Homemade Bomb

On July 4, as dozens of people were being treated mainly for leg injuries from nuts and bolts in the homemade bomb, the opposition asked the authorities not to start a "crusade" against them ahead of a parliamentary poll in September.

"Why should we tighten the screw? What has happened that we should tighten the screw?" Lukashenka said in answer to a journalist's question about the opposition plea.

"We will turn the screw on those responsible for this," he said after visiting the open air Liniya Stalina war museum about 40 kilometers west of Minsk.

Officials said on July 4 that the blast was an act of hooliganism -- a common Soviet-era phrase used to downplay such incidents. There have been no known attempts on the long-term ruler's life.

Lukashenka is banned from entry by the United States and the European Union, both of which accuse him of rigging his 2006 reelection, gagging the media, jailing opponents, and stopping protests.

Strained U.S. Relations

Relations with Washington have been strained since March when the U.S. ambassador left Belarus and embassy staff were drastically cut at the behest of Minsk over sanctions placed on Belarussian state oil products firm, Belneftekhim.

But Lukashenka said the United States had offered to help investigate the blast and Russian specialists had already arrived.

"I am grateful to the Americans for their offer. I gave an order to special services to accept this help, if it is needed," he said. "In any case, Belarussian special services are ready to collaborate."

Some EU states have said a fair election in September could transform relations with Minsk, though the continued imprisonment of an academic who ran against Lukashenka in the 2006 poll remains the key stumbling bloc to better ties.